Absorption process



May 20,'1930. c. D. COULTER ABSORPTION PROCESS `Filed Aug. 1e. 192e 4 Sheets-Sheet l ABSORPTION PROCESS Filed Aug. 16. 1926y l4 Sheets-Sheet 2 RICH 0/1. FMM wFATHER/N TANK y l Pam? F 58 Flux J0 0M METIER 7U GASILENE T11/VK wn rER ro cooL/Ns rawa Barro/1 May 20, 1930. c. D. COULTER ABSORPTION PROCESS 4 sheets-sheet 3 Filed Aug. le, 1926 VAPHRS f VAPO@ w #farm c. D. coUL-TER 1,759,346

` ABsoRPTIoN PRocElss- I May 20, 1930.

4 Sheets-Sheet 4 Filed Aug. 16 1926 i fior/Zeg.

Patented May :20,1930l UNITED STATES PATENT oFFica CLARENCE D. COULTER, or' Los ANGELES, CALIFORNIA, AssIGNOR To soUTIIwEsTEBN ENGINEERING CORPORATION, ror Los ANGELES, CALIFORNIA, A CORPORATION .OF

CALIFORNIA ABSORPTION PROCESS Application led August 16, 1926. Serial No. 129,324.

This invention relates to absorption systems, suoli for instance as are used for removing gasoline or other light hydrocarbons from natural gas. Although, as will be readily realized, the invention is not restricted to the absorption and separation of gasoline from natural gas, being applicable generally to the absorption of any vapors or mist carried in any gas, yet the invention will be most readily understood from a detailed explanation of its application to natural gas.

For some time past it has been the practice to separate gasoline or other light hydrocarbons from natural gas by an absorption process; the processes consisting mainly of bringing the vapor laden gas into contact with a heavier hydrocarbon absorbing oil, whereby the oil absorbs the light hydrocarbons and then separating the light hydrocarbons from the heavier absorbing Oil by fractional distillation and condensation.

In practicing such processes ythere have been certain difliculties encountered. Natu- Yral, gas as it comes from a Well carries in vapor or mist form not only a certain quantity of hydrocarbons that can be generallyl denoted gasoline; but also carries a quantity of hydrocarbons lighter than gasoline (having a lower boiling point than gasoline) Although in strict theory there may be no sharp dividing line, as regards vaporizing point,l between what is termed gasoline and lighter hydrocarbonsthat are not regarded asixed gases; yet, for practical purposes, there arev arbitrary dividing lines between these three classes of hydrocarbons in natural gas.l The gasoline in the natural gas may be carried either in vapor or mist form; the lighter hydrocarbons may be in vapor formand may be condensible at least to a certain extent at normal atmospheric temperature or a little In absorbing the liquefiable hydrocarbonsinto an absorbing oil it has been found diflicult to maintain conditions of temperature that Willcause the absorption ofthe desiredv gasolines without a concomitant absorption of a considerable quantity of lighter hydrocarbons: These lighter hydrocarbons are not des1red in the final product, being vaporizable at Atoo`low a temperature; but a certain quantityjo them is inevitably absorbed along with the" gasolines and must later be separated from'the gasolines. i These lighter hydrocarbons .are absorbed largely in vaporous form.;a`ndthe'y give to the laden van Object of this invention to provide a system wherein the absorbin oil, the gasolines, and the small quantity o? lighter hydrocarbonsv are cleanly separated each from the Others; so that all the gasolines are linally recovered clean and free from both the absorbing oil and the lighter hydrocarbons,- and the absorbing oil is cleaned of all its absorbed hydrocarbons to be used again in absorption. i In separating the absorbed hydrocarbons from the absorbing oil it has been found ditlicult to maintain such conditions of temperature and pressure as will vaporize all of the gasolineand not at the same time yaporize o a part of the absorbing oil. It 1s an object of this invention to maintain suoli control conditions as will cause a cleanseparationof the gasoline and'lighter hydrocarbons from the absorbing oil; so that the absorbing oil is left clean and so that the vapors then to be dealt with in the system contain no vapors of the absorbing oil. And finally, it is an Object to maintainsuch control conditions that 'the final separation of the asolines from the lighterl hydrocarbons is fean.

The method and apparatusl by which I accomplish these objects, and which are typical of my invention, are set forth in typical and preferred formy in theA following detailed 'specification and illustrated in the accompanying drawings, in which:

Fig. 1 is a diagrammatic flow sheet of the system;

Fig. 2V is a plan of that part of the apparatus which lends itself readily to being assembled upon a common base; A

Fig. 3 is a side elevation of the apparatus shown in Fig. 2; l

Fig. 4 is an end elevation of the apparatus shown in Fig. 2 (from the left hand of Fig. 2) parts being broken away and shownin section;

Fig. 5 is a sectional elevation taken as in.

ing t e construction of the reflux tower, saidl section being taken as indicated by line 9-9 on Fig. 6; and

Fig. 10 is a vertical sectional view showing the structure and arrangement of a. condenser used in the system.

It will be understood that there are Various other objects of the invention in addition to those hereinbefore set forth; but such other objects will be best understood from the following detailed description. In this description, with the aid of the accompanying drawings, I go into some particular detail as to structure and operation of the system and its various parts; but it will be understood'that I do this not for the purpose of necessarily limiting the invention to the particular details herein set out, but for the purpose of enablingthe invention itself to be well and fully understood by way of a full and detailed description of one illustrative and practical manner of carrying thel invention into effect.

In describing the method and apparatus, subject matter of this application, I shall first describe the flow of gases and liquids through the apparatus in general, having reference rst for that purpose to the flow sheet of Fig. 1.

Gas containing condensible hydrocarbons is brought to the apparatus under any suitable pressure, say from five pounds per equare inch above atmosphere or any desired higher pressure. This pressure may be obtained from the natural source or by use of a compressor plant. The rich gas is first brought through pipe 10;to a gas accumulator'A, which may comprise a simple small tank in which any solid or liquid matter is dropped out of the gas, and the accumulated matter withdrawn through pipe 9. The gas then suiiicient pressure. The pressure used is that which will cause the gases to flow through the various apparatus elements, and particularly through the absorption tower D and maintain therein the best operating pressures for gasoline absorption. Thus, the operating pressure raised at compressor C mayv vary with dil'erent circumstances and in vvarying conditions, as is well understood. A

typical pressure for absorption tower operation is about thirty pounds-per square inch above atmosphere.

Cooler B is any suitable kind of heat exchanger, for instance, a tubular heat exchanger of one or. more units. From this cooler the gas passes through pipe 17 to the bottom of absorption tower D, preferably of the bubble type. While I may use a tower of any type wherein the gas is brought into intimate contact with the absorbing oil or other medium, Iprefer to use an apparatus of the gas bubbling type, such as is shown in the application of Raymond B. Millard, S. N. 7 09,811, filed April 29, 1924, entitled Bubble tower.

The gas passes through the absorption tower and out. through the line 18 or 18 where it may be put into storage or led directly to use or discharged to atmosphere; Dry gas from the absorption tower may pass through a tail gas accumulator A1 similar to A for.

recoveringany carriedover absorption oil which can be introducedY back into the weathering tank E by means ofa trap A2 and line A3. The back pressure valve 19 maintainsa constant gas pressure on the absorber.

The oil or other absorbing medium enters the top of the tower through line 2O at approximately 70 F., passes down through the tower where it comes into intimate contact with the rising gases, absorbs all Aliquids carried in suspension or in vaporous or mist form in the gases-mainly gasoline-and accumulates at 2l in the bottom of the tower. (Further details of structure and operation are given later.) Thisl oil, with its load of gasoline, and hereinafter called rich oil, leaves the bottom of the tower through pipe 22 and goes to weathering tank E. Line 22 is controlled by valve 23 which in turn is controlled by the float mechanism 24, the function of this float controlled valve being to maintain in the bottom of the absorption tower agiven depth of rich oil7 and to feed the rich oil out of the iso will be described later.

absorption tower to the weathering tank as additionalrich oil accumulates in the bottom of the tower.

In the weathering tank the pressure may be reduced, itdcsired, by a pressure relieving valve 25 set at any desired pressure. If the pressure here is relieved to any extent, gases will come oltl through the relief valve and these gases may be discharged to atmosphere or back to suction of compressor by line 25a, or 'may bc discharged toa gas 'line or storage, as desired. The function of the weathering tank, which is merely a plain tank, is to allow absorbed gases to separate aud escape so as to further reduce the amount of light hydrocarbons in the absorbing oil and to provide a point of comparatively low pressure in the system where dephlegmator bottoms may be discharged under still pressure.

The rich oil, still cold, is then taken from the weathering tank through line 102 to pump F, known as the cold rich oil'pump, which pump forces the oil through line 2.6 to a heat exchanger G, where the rich oil 1s heated by exchange of heat from hot oil, as

may be of any suitable structure as, forinstauce, of the shell and tube type.

From heat exchanger Gr the warmed rich y oil, still under pump pressure from pump F, passes through line 27 to heater H, where it is heated to approximately 300 to 320 F., by

steam. The steam for this heater islive, dry y steam, preferably under a pressure of from 80 to 150 pounds per square 1nchfed to the heater throughA pipe 28; and the water condensate is taken from heater H through line 29 and trapl 30 to the water discharge line 31, which is a part of the water circu-` lating system and leads to water cooling tower T. y

The heated rich oil passes from heater H through line 32 into the top of an evaporator I, where the pressure is released to approximately iifteen pounds per square inch above atmosphere, and the absorbed gasoline and other lighthydrocarbons ai'e permitted to expand into vaporous form together with a small amount of absorbing oil. It will be understood that up to thev time the rich oil reaches evaporator I it has been held under such pressurev (pressure of pump F) as to hold down evaporation of the absorbedhydrocarbons, so that although the rich oil is heated to the stated temperature in heaterv H, full evaporation of the absorbed hydrocarbons does not take place until pressure is released in evaporator I. The oil pressure in heater H may be as high as titty pounds per square inch, or more. The unevaporated oil falls to the bottom of the evaporator and stands in a body at 33,y this oil being substantially freed from its former burden of light hydrocarbons. Most of the gasoline evapora- Heat exchanger Gry tion is caused by release of pressure when the liquids enter the evaporator; but in order to cause complete and clean evaporation of the lighter hydrocarbons, live steam is admitted through line 33a to the bottom of the evaporator to pass up through and agitate the oil body and to decrease the partial pressure on the oil for thc purpose of more readily evap` orating and releasing the light hydrocarbons. As a result', the light hydrocarbons are completely vaporized in the evaporator and these vapors pass off through line 34 to reflux tower J'. Further details of operation in the evaporator are given later, lparticularly pointing out how the absorbed hydrocarbon vapors are here completely separated from the abso'rbing oil.

The hot lean oil from the bottom of evaporator I passes back through line 35 to heat vexchanger Gr where it gives up apart of its Cooler L is supplied Wit-h water by lines 15a and 16 which connect into main water lines 15 and 16. Passing out oit the bottom of oil cooler L through line 20, the cooled lean oil is forced, still under pump pressure, again into the top of the absorption tower, thus completing the circulation of the absorbing oil. The charge of absorbing oil is thus continuously used in the system and only needs replenishing as small losses occur. In the evaporator, a small quantity of absorbing oil is constantly vaporized, the temperature being kept high enough in the evaporator to insure evaporation of all the light hydrocarbons, even at the expense of evaporation of a small portion of the absorbing oil; but, as hereinafter explained, this portion of the absorbing oil is also put back into the system.

In order to regulate the withdrawal of hot lean oil from the bottom of evaporator I, so that a constant suitable quantity of oil is kept at all times in the bottom ot the evaporator, a float mechanism 40 is provided in connection with the evaporator. This float mechanism, through controlling connections, diagrammatically indicated at 44, controls the steam supply through valve 45 to pump K. Pump K, as will be remembered, draws the oil from evaporator I through heat exchange G.

Instead of passing lean oil directly from heat exchange G to pump K, that lean oil may pass from the heat exchange through pipe 36 and a by-pass line 41 to storage tank P; and then pump K may draw oil from that stor-k age tank through line 42 and pipe 36, a valve 36*L in pipe v36 being closed. If this arrangerator I matically at 44". In cases where emulsion tends to form in the absorption oil the tank P acts "as a-settlingtank for removing the water. Y

The mixed vapors coming off from evapop'ass from the to of the evaporator into the ottom Vof a dep egmator consisting of a reiux tower J and a vcondenser or conthe vapors finally trol section M. The details of structure and operation of this .dephlegmator are explained hereinafter. The control section on condenser M is fed with water by lines 15b and 16", connecting with the main water lines 15 .and 16, and its function as hereinafter described is to control the temperature at which l ass from the dephlegmator; .the general unction of the dephlegmator being to cause condensation of all vapors ofy the heavier oils and thoroughly to clean the vhydrocarbon vapors (gasohne) so that no vapors except the desired asoline vapors pass to the condenser N. T e final vapors pass through pipe 50 from reflux tower J to condenser N; and the condensate passes from condenser N through line 51 and its hack pressure valve 52 to a separator O, wherein the gasoline and the water are stratified. The gasoline vapors necessarily are admixed with a certain amount of water va-` por on account of the introduction of steam into the bottom of evaporator I; and this steam is not condensed, or not wholly condensed, in the dephlegmator. When the mixed vapors emerge from evaporator'I they may ypically be at a temperature of about 290 and after passing through the dephlegmator they may typically come out to condenser N at about 180 to 210 F. In condenser N the temperature will be lowered to a point fairly well below the vaporizing temperature of any of the gasoline constituents, say to a temperature of 75 F., or, in practice, as lowas possible with the cooling water available. Typically a fairly low presi sure, say a pressure of 5 to 30 pounds per square inch, is maintained on the evaporator, the dephlegmator and the condenser; but if desired the pressures there may be still lower; the condenser may even be operated in such a manner as to create by suction a low pres- 'sure that will extend back to the evaporator, but I prefer to evaporate and condenseunder pressure. The function of valve 52 is to maintain, by proper setting, the desired pressure in the condenser and back to the evaporator.

Thel water separated in separator Y O is drawn oif through line 53' and t 54 and thence through line 55 into the bottom ofv cooling tower T, this water 'being cool enough t a in the tower. The reiiuxed and condensed oils that are thrown down in reflux tower J rough a trap t it does not have to be cooled are drawn oif from that tower through line 56' and through trap 5T and thence through line 58 to a cooler and thence either to the lean oil storage tank P or to weathering tank E. For instance, the oil line 58 may go to a coil, indicated at 59, vin the lower part of c'oolin tower T, where the reuxed oil is cooled, an

then theoil ma pass back by line 60 either to tank P or by ranch line 60` to weathering tank E. In either case, the reiluxed absorbing oil is thus put back into the system in one case at a point where the reflux oil does not pass throu h the absorption tower; in. the other case tank P) at a int where it then goes through the absorbing tower (by way of the cooler L and the line 20). Where the reflux oil from reflux tower J is clean of all absorbed hydrocarbons it may be put back iux oil may retain a small amount of ab-- sorbed hydrocarbons has no final effect on the .eiliciency of the system, as it simply means the retention in the system of a small fixed amount of absorbed hydrocarbons.

Gasoline taken off from separator O is passed through the pipe line 61 to a tank R from which the gasoline may be withdrawn from time to time as desired. The uncondensed lighter hydrocarbons pass from separator O to tank R by line 61". If it is desired to maintain on separator O and the tank R the same back pressure as is maintained on condenser N, a back' pressure valve mayl be installed at62 on tank R. i y

The gasoline line 61 running from separator O to tank R may contain what is known as a look boxy 63, a small box with a glass wall through which the gasoline may be observed. I

Water used as cooling medium in the apparatus is pumped from the bottom of the cooling tower through line 75 by a pump S into the main cold water line 16. This main cold water line connects by vbranch lines as described into the various coolers and condensers, and the hot water from them is fed back by branch lines to main hot water line 15 which discharges into the top of the cooling tower T.

I have indicated in the foregoing description the nature of the various apparatus elements. Most of these elements need no further detailed description as they are well understood by those skilled in the'art. For instance, the condensers, heat exchange or coolers, or heaters, separators, etc., will be well understood without detailed description. In fact, as to all these elements various forms may be used, as is well understood. `I-Iowever, as to the absorption tower, evaporator, the final condensers and separator; and. also as to the dephlegniator, consisting of reflux tower J and condenser or control section M, although various forms and arrangements may be'used, I desire to describe more specifically thek preferred form and arrangement of the devices I use in this system, and also to describe more in particular their operations and functions.

The details of the dephlegmator are shown in Figs. 4 Aand 6 to 9. In Fig. 4 the reflux tower portion of the dephlegmator 1s shown with a cylindrical shell 120 and with several superimposed floors 121' and 125. Although the detailed structure of the several superimposed floors may be varied, I show here a typical structure that will accomplish the operations desired in this system. For 1nstance, the reflux tower J has several upper floors 121 with central openings surrounded by notched overow rings 122; and eachvfloor supports a pan bottom 123 peripherally surrounded by a notched overflow ring 124.

The liquid that flows down through the reflux tower passes into the upper part of tle/ tower through the tube 125b into the first pan 123. Tube 125b has a sealing cup 125a at its lower end to prevent vapor passing up through it. Filling that pan and overflowing its notched edge it flows over onto the floor 121 directly below and, rising to a sufficient level on that floor, it overflowsv the inner notched ring 122 in that floor and flows down onto the next pan 123; and so on through the various floors. Where the liquid flows over the notched rings it is showered through the gases that are passed upwardly through the reflux tower, as will be hereinafter described.

Below the floors just described, there are several superimposed floors 125 that have a different type of apparatus for causing intimate admixture of the gases and liquids. This type of. apparatus hereinafter-briefly described is fully set forth and is the subject mattei' of the aforesaid application of Raymond B. Millard. A plan of one' ofthe floors and its apparatus is shown in Fig. 6. Fig. 7 shows an enlarged detail cross sect-ion of some of the elements; and Fig. 8 shows some of the elements in perspective sectional detail. Each of the floors 125 extends around the inner periphery of shell 120 and is bounded at its inner edge by a vertical wall 126.

In fact the floor 125 may be said to form only a ledge around the inside of the shell, interiorly bound by wallv 126. Inside the wall 126 the gas and liquid -admixingelements may be composed of upwardly facing channels 127 whose upwardly extending flanges 128 are s aced apart to provide spaces 129 through which the gases and vapors may flow upwardly. Over each pair of spaced eh annel flanges 128 there is an inverted chan nel 130 whose depending flanges 131 are spaced from flanges 128 so that the gas that flows upwardly between flanges 128 may flow over the upper edges of those flan es and downwardly through the .spaces etween flanges 131 and 128. Flanges 131 are provided with perforations 132 through which the gas and vapor may flow by depressin the liquid level to such a point as indicate at L in Fig. 7 the liquid level being depressed by the gas afnd vapor pressure so that the gases and vapors can pass through perforations. 132 and bubble upwardly through the liquid that stands in the space between flanges 131, that liquid standing there at such a level as indicated at L1. The liquid is fed into the liquid holding spaces by being dropped down above the inverted channel 130; and the liquid flows from each floor by passing out endwise from each space between flanges 131, through openings '133 in wall 126, these openings 133vregistering with the spaces between flanges 131, as is indicated in Fig. 8. Both the channels 127 and 13() abut endwise againstwall 126 and are welded or otherwise attached thereto so as to make a liquid tight joint therewith. The liquid that flows through openings 133 in wall 126 flows onto the floor 125 outside wall 126 and then, having risen to a suliicient level on floor 125, overflows the adjustable overflow collar 135 o f overflow nipples 136 which direct the liquid downwardly into a trough 137 below the floor. Trough 137 below each floor is arranged in a direction lengthwise of the channels of that particular floor, as will be seen by noting the trough shown in dotted lines in Fig. 6. The trough 137 that takes the overflow from the floor above is, however, arranged crosswise of the channels of the floor immediately below (note the trough 137 shown in full lines in Fig. 6). Each trough may be provided with perforations in its bottom as shown at 138 in Fig. 6, and may also be provided with notches 139 along its edges as shown in Fig. 9. The trough, taking the liquid overflow from the floor above, distributes that liquid overflow equally to the central parts of all the channels of the floor next below; and the liquid thus distributed to the central parts of the channels flows outwardly towards the ends of the channels and then overflows into the trough next below to go to the floor next below. While passing through the channels the upwardly flowing gas and vapors bubble through the liquids and thus there is caused an intimate commingling of the gases and vapors and the liquids'.

In the reflux tower here described this intidown through the gases and vapors'. A1- though the system here described is not necessarily limited to these particular details, yet I find that a reflux tower equipped in this manner is very eiiicient for the purposes herein set forth.v v

Condenser M directly above reilux tower J (condenser M and reflux tower J forming together the dephlegmator of the system) is of the same type as shown in Flg. 10, which is a showing of the inal condenser N. Such a condenser is composed of cooling fluid tubes 140'extending across a vertical vapor passage 141, the ends of the tubes communicating with passages or compartments containedwithin .cover plates 142. And these cover plates being provided with division walls 143 arranged so that the .cooling water that enters by pipe 16b first passes across through v a certain number of tubes 140,' enters a compartment 142'* in one of the cover plates, returns to compartment 142b of the other cover plate through a certain number of tubes, then is turned back to compartment 142c by certain other tubes, and so on, finally flowing through the last division of tubes into com,- partment 142d and out through pipe 15". In such a condenser (I am describing this condenser as the condenser N, but its structure is the same as condenser M) the vapors and gases enter from above through pipe and pass outwardly through the vertical vapor passage 141 of the condenser, the condensate and any uncondensed gases andvvapors pass-V ing out from the condenser through pipe 5.1. In the condenser itself the vertical vapor passage is relatively large and free; and the condensate forms in small drops on the cooling tubes; and the space inside the condenser being relatively large and free there is little enforced commingling of the vapors and liquids. The vapors and gases flow quietly and slowly; there is little turbulence.

Assuming that condenser M of the Vde- 'phlegmator is the same as condenser N shown in Fig. 10, it will be seen that the condensate from condenser M passes directly downwardly from that condenser through the vertical tube 145 into a compartment 146 in the upper end of reflux tower J The uncondensed gases and vapors are fed to the reflux tower kfrom evaporator I into the lower part of the reflux tower through pipe 34 (see Figs. 1

and 2) 'which pipe enters the refluxV tower at the point 34 (see Fig. 4) under the lowermost floor 125. The gases pass upwardly through the several oors and through the hereinbefore described apparatus, and finally the gases and vapors pass from the space above uppermost floor 121, out of the reiiux tower and up through pipe 147 and into the top of condenser M. In this condenser M a detinite control temperature (say 205-210 F.) is maintained so that all the heavier Vconstituents of the' vapors are condensed while the lighterA vapor constituents are left in vapor state. In the vapors that reach the reiiux tower there are, roughly speaking, -three classes. First the vapors lof what may be termed gasoline; second, the vapor of hydrocarbons lighter and more volatile than gasoline, and third, the vapors of hydrocarbons heavier and less volatile than gasoline, the last class consisting mainly of absorbing oil vapors. (There is also water vapor, but that may be for the moment ignored.) The temperature control in condenser M is maintained at such-a point that the absorbing oil vapors are condensed while all the vapors of the two lighter classes are left uncondensed. The condensed and the uncondensed vapors and also whateveriixed gases there may be pass downwardly through condenser M and into upper chamber 146 of reiiuxtower ass il. In passing downwardly through the con-I denser there is a minimum of admixture of the vapors and liquids; the liquids gather on floor 146of chamber 146 and immediately flow downwardly through tube 12511 onto the uppermost licor 121. The uncondensed vapors in chamber 146 flow out from that chamber through pipe 50 to condenser N to be finally condensed. v

But these vapors that :finally low out from chamber 146 are clear of all heavier condensate; andthe heavier condensate that finally flows out `from the bottom of reflux tower J Y is substantially clear of all lighter vapors owing to the action that takes place in the lowerppart of the reiiux tower. T he initial mixed vapors that enter at point 34a at the lower end of the reflux tower are constantly passing up through and in intimate admixture with the downwardly flowing condensate, which condensate is at a temperature lower than the upwardly passing vapors. These upwardly passing vapors, which have not as` yet been passed through condenser M, contain vapors of the heavier constituents as well as vapors of the lighter constituents. By contact with the cooler heavier condensate a certain amount of the heavier vapors are condensed. as the mlxed lvapors pass up the dephlegmator as I have described it, theremay be a constant revaporization ofcertain constituents in the lower part ofthe reflux tower, those vapors passing up the condenser and then a'constant recondensation of those constituents to be passed'downwardly into the lower part of the reflux tower as liquid,

where they may again be revaporized. This constant circulation of vapors of a certainv class, andthe constant intimate admixture of the vapors and liquids, washing'the light-er vapors out of the iquids and washing the heavier condensate mist out of the vapors, results in a very definite and clean separationof the'heavier condensate fromjthe lighter vapors, so that substantially nothing but vapors of the two lighterclasses hereinbefore, enumerated finally pass off from the dephleglighter c asses, viz, vvapors o what may be.l

termed aspolinel and vaporsofjhydrocarbons ligtervthan gasoline.v and-whichit is wished-to"separate from the asoline; and watervapolnf,l As these. mixe vapors pass down through condenser NA the gasoline and watervapors are condensed, the temperature in condenser N being maintained at a proper point (say As beforestated, the vapor passage of condenser N is relatively large and open and as the vapors pass around cooling tubes 140 the condensate forms in small drops on the tubes, leaving the vapor passage relatively open and u nobstructed; so that'in the condenser there is relatively little enforced agitation'and admixture of the condensate with the uncondensed vapors. As the condensate drops to the bottom of the vapor passage it flows off throughvpipe 51. This pipe 51 is made of sufficient size to carry ofi' the condensate without filling the pipe to capacity so that the vapors that also pass down through the condenser and out through pipe 51 can pass out through the upper part of the ipe without being enforcedly admlxed with t e condensate. For this purpose pipe 51, as shown in detail in Fig. 10, is arranged with a -horizontal'run directly below condenser N and has no traps or pockets in it; so that the liquid can run off through the pipe at such a level as is indicated at L2, and the vapors can flow through the same pipe above the liquid. Thus when liquid and vapors emerge into separator O the liquid may immediatelydrop down toward the bottom of the separator and the uncondensed vapors and gases may immediately rise without being intermingled with vthe liquid. In fact, as is shown best in Fig. 3, the entrance point' of pipe 51 to the separator is very little above the level where the gasoline pipe 61 leads off' from the separator, so that the liquid fiowing from `pipe 51 into the separator falls but a very little distance through the vapors standing above the liquid in the separator. The vapors then flow out of the 'upper end of the separator-through pipe .61l1 and the gasoline through pipe 61, both the gases and liquids going separately to the gasoline tank R where the liquids stand in the'bottom and the uncondensed vapors stand above the gasoline. As before stated,.

a back pressure valve. 62 may be placed on gasoline tank R and this back pressure valve may be utilized "to maintain on the whole system' back to and including evaporator I, a suitable voperating pressure, say 15 or 20 ypounds per square inch `above atmosphere.

If the gasoline tank R is not capable of withstanding this pressure, valve 62 may be set.

at a lower pressure and back pressure valve 52 at the outlet of condenser N may b e set` to hold the desired pressure on the apparatus behind it. The advantage of holding a pressure on the, gasoline tank R and of utilizing the unconde'nsed vapors to stand over the gasoline in that tank is that unnecessary evaporation'of the gasoline is thus prevented and a considerable quantity of gasoline thus saved.

Going back further into the system for the purpose of explaining its process -in generalv I note that absorption tower D is equipped with superimposed bubbling fioors 125, similar in arrangement and construction to fioors v125 described in connection with refiux tower J. Also evaporator I is' equipped with similar superimposedfloors 125. (Figs. 5, '69 v may be takento be details of the absorber and -evaporator as well as of the reflux tower.)

These fioors are indicated in dotted lines in p the absorber and evaporator in Fig. 1. In the absorber the action of the su erimposed floors is to cause the upwardly owing gas to be bubbled intimately through the downwardlyV fiowing absorbing oil; the oil picking up all or substantially all of the gasoline carried by l the gas. It is one of the features of operation of an absorption tower of this type and character that, operating at a certain controlled temperature (say 70 F.) it causes the absorbing oil to pick up practically all of the hydrocarbons condensible at that temperature, but a very small fraction of hydrocarbons that condense at a lower temperature. In other words the hydrocarbons picked up bythe absorbing oil in the absorption tower are, in this particular instance, very purely gasoline, `only a small precentage of lighter hydrocarbons being picked up. The vapor or gas pressure of the rich or laden absorbing oil is, therefore, comparatively low; and therev is comparatively little of the very light vapors to be finally separated from the final gasoline condensate. the absorption tower are found in the fact-s that both the absorbing oil and the incoming vapor laden gases are cooled to a uniform absorption operating temperature before being put into the absorption tower; and also The reasonsV for this action ofl 'in theA fact thatthe gases and liquids are.

passed and re-passcd many times'into and rout of contact with each other in their passages through the absorption tower. I n other words, the gases are thoroughlywashed in the absorbing oil many times over; and all hydrocarbons condensible at the operating temperature and 'pressure are absorbed by the oil, while ractically all hydrocarbons vaporizable at t 1e operating tempearture and pressure are washed out of the Aoil by the gases.

' Any suitable pressure may be maintained on v and' separator O.

t-he bottom o the absorber. A pressure of about three pounds will operate such a tower,

but in practice a pressure of about thirty Iny evaporator I, which is equipped also with oors 125, as before explained, the hot rich oil heated to the proper temperature in heater H and under a pressure say of about fifty pounds per square inch above atmosphere, has its pressure released to the lower pressure maintained by back pressure valve 52 or 62, with the result that the lighter hydrocarbons carried 'in the absorbing oil are vaporized almost completely. In practice, a

l pressure of five to twenty-five pounds gauge may be carried; butl the pressure release to this lower ressure is not sudden but gradual, controlled y the gradual evaporation of the liquids and by the eiect of the steam affecting the partial pressure.

All the vapors thusgenerated in the upper part of evaporator I pass immediately out ofthe evaporator through line 34 to the reflux tower. Due to the impossibility in practice of maintaining temperatureand pressure conditions such as will in a single evaporation operation cause clean separation between vapors of lighter and heavier hydro-carbons, ofcourse there is a small fraction of the absorbing oil also vaporized in the upper part of the evaporator; and so a small fraction of heavier vapors passesto the reflux tower' along withthe vapors of the lighter hydrocarbons, to be separated from the vapors of the lighter hydrocarbons, as before explained, by the action in the dephlegmator, of which the reflux tower forms a part. But in the' evaporator not all of the lighter hydrocarbons will be immediately vaporized or will immediately pass oil' as vapors. The unvaporized heavy absorbing oil passes down through the evaporator, carrying with it any small unvaporized portion of the lighter hy-y drocarbons and also inevitably carrying down with ita small fraction of the lighter vapors which it entraine. These unvaporized absorbing oils then pass down through the various floors `125 of the evaporator and are met evaporator and passing up through the downwardly owing and cooler absorbing oil; and those vapors wash `the absorbing oil of any entrained lighter hydrocarbon fvaporsg and also heat it so vas to keep up its temperature to evaporatev any lighter hydrocarbons thatmaybe carried ,down lin liquid form in the absorbing. oil. And at the same time, the

cooler absorbing oilswash out of the vaporsv any vaporsor mist of heavy oil; .making the vapors as clean as possible. Thus before'the absorbing oil finally passes out o the evaporator, it is by reflux action and steaming entirely freed of all lighter hydrocarbon vapors, which lighter vapors join the lighter vapors passing out at the upper end of the evaporator. Thus in the evaporator all lighter hydrocarbons are entirely taken out of the absorbing oil so that the absorbing oil that then goes to the oil coolers to pass back to the absorption tower is entirely or substantially freed of lighter hydrocarbons itA has picked up in the absorption tower.

To recapitulate briefly: It' will be seen that Vin this system the original action in the ab.

sorbing ltower -is to the elect that the absorbing oil picks up from the original laden gas practically all of the hydrocarbonsof a certain character. and a minimum of hydrocarbons lighter than that. Then by the .action of the system and particularly by the action in the evaporator, allfofthe lighter hydrocarbons are separated by evaporation from the absorbing oil, for this purpose a small part ofthe absorbing oil beingv also evaporated. Thus the absorbing oil is freed substantially entirely of its previouslyabsorbed lighter hydrocarbons. Next the function and operationof the dephlegmator (reflux tower J and condenser M) is to entirely separate from themixed vapors allv the heavier hydrocarbons (the small percentage of absorbing oil vapors in the mixed vapors), leaving only the vapors of the desired hydrocarbons and a small proportion of still lighter hydrocarbons to go to the final condenser. Then the function and operation of the final condenser and separator is to separate cleanly the desired hydrocarbons, in form of a condensate, from the lightest hydrocarbons which are not desired in thefinal product.

I have spoken before of the fact that, in this system,'as retention of a small amount of absorbed hydrocarbons in the reflux absorbing oil does not affect the final efficiency of its gasoline recovery.

In general practice it is hydrocarbons that freely vaporize at normal atmospheric temperature that are not desired in the final product. The desirable final product hydrocarbons, such as gasoline, do not freely vaporize at normal atmospheric temperature, but, of course, have an appreciable vapor pressure at that temperature'. At the operating temperatures and pressure indicated throughout the system as described, the final liquid product produced is one of the nature of gasoline; while the nal vaporous product separated from the gasoline is one that will not condense at normal atmospheric temperature.

Consequently the final separated uncondensed vapor may be used to maintain a suitable vapor pressure over the final stored gasohne to prevent slow evaporation of the gasoline, without the lighter vapors condensing into the gasoline in the storage tank.

From the foregoing description of the system in general, it will be seen that it has certain further advantageous features of operation. In so far as can be accomplished, the heat of the system is kept within the system by heat interchange between relatively hot and cool fluid; and heat is supplied from the outside to the system only at evaporator I and heater H, which immediately precedes the evaporator; in other words, heat is supplied from the outside to the system only for the purpose of evaporating the lighthydrocarbons. The heat there supplied to the system is so transferred to the fluids and other parts of the system as to conserve the supply of heat as far as possible. For instance, the hot lean oil passing away from evaporator I at a temperature of say 290O F. is first made to give up a part of its heat, in heat exchange G, to the rich oil that is passing to heater H. The rich oil going to heater H is thus pre'- liminarily warmed to as high a temperature as practicable (say about 240o F.) by taking heat away from the hot lean oil. The lean oil is thus cooled as much as practicable, so that the minimum amount of heat has to be taken away from the lean oil by water cooling in cooler L, where the lean oil is cooled to approximately F. for efficient operation in absorption tower D. The oil used in absorption tower D necessarily comes out at approximately F. In order further to save heat within the system, the cold rich oil flowing from pump F, instead of going directly through line 26 to heat exchanger Gr, may go entering heat exchanger Gl may be substan-4 tially higher than say 70 F., with the result that the rich oil is warmed to still higher temperature in the heat exchanger.

Another of the features of the apparatus a herein described is that it is capable of being. arranged and mounted in a very compact arrangement on a single base, so as to be easily transported if desired. In oil field practice 1t is quite common that natural gas will be produced in comparatively large quantities in a given locality, but for only a short period of time. A portable absorbing system is, therefore, of much practical use. The system as here illustrated lends itself very readily to compact and portable arrangement, the whole system, with the exception of the cooling tower, the compressor, the absorber and the tanks, being mounted upon a single portable base. Suchan arrangement is shown in Figs. 2 to 5 inclusive.

Here is a suitable base, preferably made up of steel beams, illustrated at 90, and on it the various elements of the apparatus are mounted. In the plan of Fig. 2 heater H is shown mounted directly above the evaporator I which stands upon base 90. The gasoline and water separator O is shown mounted alongside evaporator I, with the look box 63 arranged in a convenient position and at a convenient height alongside the evaporator. Gas cooler B is shown mounted on the base near one corner 'and directly above it is the gas scrubber Bl--and directly above that and mounted on the scrubber is the condenser N. At the same end, but at the other corner of the base is mounted the reflux tower J, with its condenser or temperature control unit M mounted directly above it. At the other side of the evaporator I from the reflux tower are mounted -the oil cooler L and the heat exchanger Gr; and the various pumps are mounted in a line at the end of the base. Two water pumps S are provided so that either or both may be operated. They take cold water 'from the lcooling tower through line 75 and pump it through main cold water line 16 from which various branch cold water lines run to the coolers and condensers as shown inFigs. 2 to 5, inclusive, the various branch lines being there indicated by the same numerals as in Fig. 1. The hot water from the various coolers and condensers passes through the several branch lines indicated by numerals the same as in Fig. 1 to the main hot water line 15 (see Figs. 2, 3 and Ll) that is adapted at its upper end to beextended to the'cooling tower. The gas first enters the apparatus shown in Figs. 2 to 5 by entering scrubber 'B1 at the flanged opening 100 of the scrubber. From the scrubber gas passes directly to the gas cooler B which is directly below the scrubber and then the gas passes out of the bottom of gas cooler B, through the pipe connection 11 to the absorbing tower which is not mounted ioo on the base with the rest of the apparatus. Below gas cooler B a `drain 101 is shown to take drainage from the gas cooler (see F1gs.

`3 and l and corresponding diagrammatic showing on Fig. 1). From the absorption tower the gas, as before mentioned, passes oftl to mains or to storage as may be desired-the gas does not again enter the apparatus. The rich oil from the absorption tower, as before pointed out, goes next to the weathering tank which is also mount-ed independently of the unit assembled apparatus; and then from the weathering tank the rich oil goes to pump F. In Fig. 2 the entry of the cold rich oil from the weathering tank is shown through pipe 102 to pump F. From pump F the cold rich oil, as before described, goes through line 26 to heat exchange G; and pipe 26 leading from pump F to the heat exchange is also shown in Fig. 2. Figs. 2, 3 and 5 show the pipe 27 that leads the warm rich oil from heat exchange G to heater H; and from heater H the How of the hot rich oil to evaporator I .is through pipe 32 as shown in Figs. 2, 3 and 5. From the evaporator the vapors go through pipe 34 (shown only inl Fig, 2) to the bottom of reiux tower J and the inal vapors from the reiiux tower (after having been treated in the reiux toweras before described) go through pipe (Figs. 2, 3, 4 and 5) to condenser N. Figs. 2 and 3 show best pipe 51, separator O, the pipe system 61, look box .63, etc., that take the condensate of condenser N and separate it and pass the gasoline through pipes 61 to the gasoline tank and the water through pipe 53 ofi' to the water system before described.

From the reflux tower J the pipe 56 leads the condensed oils back to the oil system as before described (shown in Fig. 2). From evaporator I the hot lean oil oes by pipe 35 to heat exchange G, that pipe eing shown in Figs. 2, 3 and 5; and the pipe 36 that takes lean oil from heat exchange G to pump K is shown in Fi 2. From pump K the pipe 37 is shown in Figs. 2 and 3 going to oil cooler L and from oil cooler L the pipe 20 that takes the cooled lean oil to the absorption tower is shown in Figs. 2, 3 and 5.

The various other details of apparatus elements and connective pipes are also shown on Figs. 2 to 5,v indicated by their proper numerals, directions of flow being indicated by arrows, and legends being attached to indicate the various iuids fiowing through the pipes; and all of this will be understood from what has previously been said in the description of ig. 1. In Fig. 2 an additional pump Y is shown, and valve controlled pipe connections indicatedv generally by the numeral 110 are arranged so that the additional pump can be used as a substitute for either pump lF or pump K. All of the pumps are connected to a common steam line 111, and steam lines 28 and 33a are connected into steamv line 111 1. A process `of recovering gasolines from. l

natural gas, that includes absorbing from the gas and into a heavy absorbing oil all hydrocarbons condensible at a predetermined temperature, and during such absorption intimately commingling the gas and the absorbing oil and washing each in the other and thereby minimizing the absorption of hydrocarbons that normally condense at a temperature lower than said predetermined temperature, said gas and absorbing oil being' maintained at approximately said predetermined temperature during the absorption operation; heating the laden absorbing oil and vaporizing its absorbed hydrocarbons and a portion of the absorbing oil, and thereby removing from theabsorbing oil substantially all of its absorbed hydrocarbons; cooling and fractionally condensing the mixed vapors resultantfrom said evaporative action and thereby selectively condensing the absorbing oil vapors from said mixed vapors, returning the condensed absorbing oil to the main body of absorbing oil in the system after said absorbing oil'has left the absorption operation and before it reaches the heating stage; and again cooling and fractionally condensing `the resultant vapors to condense the gasoline vapors and leave the still lighter hydrocarbon vapors in vaporous form, said condensing action being carried on so that the gasoline condensate is not forcibly mixed with the uncondensed vapors; and rmly y separating the condensate from the uncondensed vapors.

2. A'process of recovering gasolines from vnatural gas, that includes absorbing from the gas and into a heavy absorbing oil all hydrocarbons condensible at a predetermined temperature, and during such` absorption intimately commingling the gas and the absorb- -ing oil and washing each in the other and thereby minimizing the absorption of hydrocarbons that normally condense at a temperature lower than said predetermined temperature, said gas and absorbing oil being maintained at approximately said predetermined temperature during the absorption operation, said absorption operation being carried on under pressure, then relieving the pressure on the laden absorbing oil without substantially changing its temperature and thereby releasing some of the vapors of the lighter absorbed hydrocarbons; and thenv heating-the laden absorbing oil after the said pressure reduction thereof and vaporizing its absorbed hydrocarbons and a portion of the absorbing oil, and thereby removing from the absorbing oil substantially all of its absorbed hydrocarbons; cooling and fractionally condensing the mixed vapors resultant from said evaporating action and thereby selectively condensing the absorbing oil vapors from said mixed vapors, `returning the condensed absorbing oil to the main body of absorb-ing oil in the system aftersaid absorbing oil has left the absorption operation; and again cooling and fractionally condensing the resultant vapors from said fractional condensing action, said condensing action being carried on so that the gasoline condensate is not forcibly mixed With the uncondensed vapors; and finally separating the condensate from the uncondensed vapors.

3. The process of recovering gasoline fractions from gas, that includes absorbing said fractions in comparatively heavy absorbing liquid; then heating the laden absorbing liquid to a temperature suiicient to vaporize the absorbed substancesand also a portion of the absorbing liquid; then by fractional condensation separating substantially all the vapors of the absorbed liquid; and putting said absorbing liquid condensate back into the body of absorbing liquid in the process at a point subsequent to the absorption operation and before the heating stage.

In Witness that I claim the foregoing I have hereunto subscribed my name this 24th day of July, 1926.

CLARENCE D. COULTER. l

CERTIFICATE oF CORRECTION.

Patent No. 1,759,346. Granted May 20, 1930, to

CLARENCE D. COULTER.

It is hereby certified that error appears .in the printed specification of the above numbered patent requiring Acorrection as follows: Page 10, Ime 104, claIm 1, for the word "firmly" read "finally"; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case inthe Patent Office.

Signed and sealed this 22nd day of July, A. D. 1930.

Wm. A. Kinnan, l Acting Commissioner of Patents.

(Seal) 

